Prevent UI events during footprint dialog ctor

Errors may get thrown when the 3d models are loaded for missing search
paths.  This triggers the idle event that makes assumptions about the
state of the dialog.  We halt event handling until the ctor finishes.

Fixes https://gitlab.com/kicad/code/kicad/issues/12944

(cherry picked from commit be86e9f57f)

pcbnew/dialogs/dialog_footprint_properties_fp_editor.cpp

@@ -137,6 +137,7 @@ DIALOG_FOOTPRINT_PROPERTIES_FP_EDITOR::DIALOG_FOOTPRINT_PROPERTIES_FP_EDITOR(
     m_gridSize( 0, 0 ),
     m_lastRequestedSize( 0, 0 )
 {
+    SetEvtHandlerEnabled( false );
     // Create the 3D models page
     m_3dPanel = new PANEL_FP_PROPERTIES_3D_MODEL( m_frame, m_footprint, this, m_NoteBook );
     m_NoteBook->AddPage( m_3dPanel, _("3D Models"), false );
@@ -221,6 +222,7 @@ DIALOG_FOOTPRINT_PROPERTIES_FP_EDITOR::DIALOG_FOOTPRINT_PROPERTIES_FP_EDITOR(
     SetupStandardButtons();
 
     finishDialogSettings();
+    SetEvtHandlerEnabled( true );
 }